/*
 * Copyright (c) 2008, 2013, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
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 *
 *
 *
 *
 *
 *
 *
 */

package java.lang.invoke;

import sun.misc.Unsafe;
import java.lang.reflect.Method;
import java.util.Arrays;
import sun.invoke.util.VerifyAccess;

import static java.lang.invoke.MethodHandleNatives.Constants.*;
import static java.lang.invoke.LambdaForm.*;
import static java.lang.invoke.MethodTypeForm.*;
import static java.lang.invoke.MethodHandleStatics.*;

import java.lang.ref.WeakReference;
import java.lang.reflect.Field;
import sun.invoke.util.ValueConversions;
import sun.invoke.util.VerifyType;
import sun.invoke.util.Wrapper;

/**
 * The flavor of method handle which implements a constant reference
 * to a class member.
 *
 * @author jrose
 */
class DirectMethodHandle extends MethodHandle {

  final MemberName member;

  // Constructors and factory methods in this class *must* be package scoped or private.
  private DirectMethodHandle(MethodType mtype, LambdaForm form, MemberName member) {
    super(mtype, form);
    if (!member.isResolved()) {
      throw new InternalError();
    }

    if (member.getDeclaringClass().isInterface() &&
        member.isMethod() && !member.isAbstract()) {
      // Check for corner case: invokeinterface of Object method
      MemberName m = new MemberName(Object.class, member.getName(), member.getMethodType(),
          member.getReferenceKind());
      m = MemberName.getFactory().resolveOrNull(m.getReferenceKind(), m, null);
      if (m != null && m.isPublic()) {
        assert (member.getReferenceKind() == m.getReferenceKind());  // else this.form is wrong
        member = m;
      }
    }

    this.member = member;
  }

  // Factory methods:
  static DirectMethodHandle make(byte refKind, Class<?> receiver, MemberName member) {
    MethodType mtype = member.getMethodOrFieldType();
    if (!member.isStatic()) {
      if (!member.getDeclaringClass().isAssignableFrom(receiver) || member.isConstructor()) {
        throw new InternalError(member.toString());
      }
      mtype = mtype.insertParameterTypes(0, receiver);
    }
    if (!member.isField()) {
      if (refKind == REF_invokeSpecial) {
        member = member.asSpecial();
        LambdaForm lform = preparedLambdaForm(member);
        return new Special(mtype, lform, member);
      } else {
        LambdaForm lform = preparedLambdaForm(member);
        return new DirectMethodHandle(mtype, lform, member);
      }
    } else {
      LambdaForm lform = preparedFieldLambdaForm(member);
      if (member.isStatic()) {
        long offset = MethodHandleNatives.staticFieldOffset(member);
        Object base = MethodHandleNatives.staticFieldBase(member);
        return new StaticAccessor(mtype, lform, member, base, offset);
      } else {
        long offset = MethodHandleNatives.objectFieldOffset(member);
        assert (offset == (int) offset);
        return new Accessor(mtype, lform, member, (int) offset);
      }
    }
  }

  static DirectMethodHandle make(Class<?> receiver, MemberName member) {
    byte refKind = member.getReferenceKind();
    if (refKind == REF_invokeSpecial) {
      refKind = REF_invokeVirtual;
    }
    return make(refKind, receiver, member);
  }

  static DirectMethodHandle make(MemberName member) {
    if (member.isConstructor()) {
      return makeAllocator(member);
    }
    return make(member.getDeclaringClass(), member);
  }

  static DirectMethodHandle make(Method method) {
    return make(method.getDeclaringClass(), new MemberName(method));
  }

  static DirectMethodHandle make(Field field) {
    return make(field.getDeclaringClass(), new MemberName(field));
  }

  private static DirectMethodHandle makeAllocator(MemberName ctor) {
    assert (ctor.isConstructor() && ctor.getName().equals("<init>"));
    Class<?> instanceClass = ctor.getDeclaringClass();
    ctor = ctor.asConstructor();
    assert (ctor.isConstructor() && ctor.getReferenceKind() == REF_newInvokeSpecial) : ctor;
    MethodType mtype = ctor.getMethodType().changeReturnType(instanceClass);
    LambdaForm lform = preparedLambdaForm(ctor);
    MemberName init = ctor.asSpecial();
    assert (init.getMethodType().returnType() == void.class);
    return new Constructor(mtype, lform, ctor, init, instanceClass);
  }

  @Override
  BoundMethodHandle rebind() {
    return BoundMethodHandle.makeReinvoker(this);
  }

  @Override
  MethodHandle copyWith(MethodType mt, LambdaForm lf) {
    assert (this.getClass() == DirectMethodHandle.class);  // must override in subclasses
    return new DirectMethodHandle(mt, lf, member);
  }

  @Override
  String internalProperties() {
    return "\n& DMH.MN=" + internalMemberName();
  }

  //// Implementation methods.
  @Override
  @ForceInline
  MemberName internalMemberName() {
    return member;
  }

  private static final MemberName.Factory IMPL_NAMES = MemberName.getFactory();

  /**
   * Create a LF which can invoke the given method.
   * Cache and share this structure among all methods with
   * the same basicType and refKind.
   */
  private static LambdaForm preparedLambdaForm(MemberName m) {
    assert (m.isInvocable()) : m;  // call preparedFieldLambdaForm instead
    MethodType mtype = m.getInvocationType().basicType();
    assert (!m.isMethodHandleInvoke() || "invokeBasic".equals(m.getName())) : m;
    int which;
    switch (m.getReferenceKind()) {
      case REF_invokeVirtual:
        which = LF_INVVIRTUAL;
        break;
      case REF_invokeStatic:
        which = LF_INVSTATIC;
        break;
      case REF_invokeSpecial:
        which = LF_INVSPECIAL;
        break;
      case REF_invokeInterface:
        which = LF_INVINTERFACE;
        break;
      case REF_newInvokeSpecial:
        which = LF_NEWINVSPECIAL;
        break;
      default:
        throw new InternalError(m.toString());
    }
    if (which == LF_INVSTATIC && shouldBeInitialized(m)) {
      // precompute the barrier-free version:
      preparedLambdaForm(mtype, which);
      which = LF_INVSTATIC_INIT;
    }
    LambdaForm lform = preparedLambdaForm(mtype, which);
    maybeCompile(lform, m);
    assert (lform.methodType().dropParameterTypes(0, 1)
        .equals(m.getInvocationType().basicType()))
        : Arrays.asList(m, m.getInvocationType().basicType(), lform, lform.methodType());
    return lform;
  }

  private static LambdaForm preparedLambdaForm(MethodType mtype, int which) {
    LambdaForm lform = mtype.form().cachedLambdaForm(which);
    if (lform != null) {
      return lform;
    }
    lform = makePreparedLambdaForm(mtype, which);
    return mtype.form().setCachedLambdaForm(which, lform);
  }

  private static LambdaForm makePreparedLambdaForm(MethodType mtype, int which) {
    boolean needsInit = (which == LF_INVSTATIC_INIT);
    boolean doesAlloc = (which == LF_NEWINVSPECIAL);
    String linkerName, lambdaName;
    switch (which) {
      case LF_INVVIRTUAL:
        linkerName = "linkToVirtual";
        lambdaName = "DMH.invokeVirtual";
        break;
      case LF_INVSTATIC:
        linkerName = "linkToStatic";
        lambdaName = "DMH.invokeStatic";
        break;
      case LF_INVSTATIC_INIT:
        linkerName = "linkToStatic";
        lambdaName = "DMH.invokeStaticInit";
        break;
      case LF_INVSPECIAL:
        linkerName = "linkToSpecial";
        lambdaName = "DMH.invokeSpecial";
        break;
      case LF_INVINTERFACE:
        linkerName = "linkToInterface";
        lambdaName = "DMH.invokeInterface";
        break;
      case LF_NEWINVSPECIAL:
        linkerName = "linkToSpecial";
        lambdaName = "DMH.newInvokeSpecial";
        break;
      default:
        throw new InternalError("which=" + which);
    }
    MethodType mtypeWithArg = mtype.appendParameterTypes(MemberName.class);
    if (doesAlloc) {
      mtypeWithArg = mtypeWithArg
          .insertParameterTypes(0, Object.class)  // insert newly allocated obj
          .changeReturnType(void.class);          // <init> returns void
    }
    MemberName linker = new MemberName(MethodHandle.class, linkerName, mtypeWithArg,
        REF_invokeStatic);
    try {
      linker = IMPL_NAMES
          .resolveOrFail(REF_invokeStatic, linker, null, NoSuchMethodException.class);
    } catch (ReflectiveOperationException ex) {
      throw newInternalError(ex);
    }
    final int DMH_THIS = 0;
    final int ARG_BASE = 1;
    final int ARG_LIMIT = ARG_BASE + mtype.parameterCount();
    int nameCursor = ARG_LIMIT;
    final int NEW_OBJ = (doesAlloc ? nameCursor++ : -1);
    final int GET_MEMBER = nameCursor++;
    final int LINKER_CALL = nameCursor++;
    Name[] names = arguments(nameCursor - ARG_LIMIT, mtype.invokerType());
    assert (names.length == nameCursor);
    if (doesAlloc) {
      // names = { argx,y,z,... new C, init method }
      names[NEW_OBJ] = new Name(Lazy.NF_allocateInstance, names[DMH_THIS]);
      names[GET_MEMBER] = new Name(Lazy.NF_constructorMethod, names[DMH_THIS]);
    } else if (needsInit) {
      names[GET_MEMBER] = new Name(Lazy.NF_internalMemberNameEnsureInit, names[DMH_THIS]);
    } else {
      names[GET_MEMBER] = new Name(Lazy.NF_internalMemberName, names[DMH_THIS]);
    }
    assert (findDirectMethodHandle(names[GET_MEMBER]) == names[DMH_THIS]);
    Object[] outArgs = Arrays.copyOfRange(names, ARG_BASE, GET_MEMBER + 1, Object[].class);
    assert (outArgs[outArgs.length - 1] == names[GET_MEMBER]);  // look, shifted args!
    int result = LAST_RESULT;
    if (doesAlloc) {
      assert (outArgs[outArgs.length - 2] == names[NEW_OBJ]);  // got to move this one
      System.arraycopy(outArgs, 0, outArgs, 1, outArgs.length - 2);
      outArgs[0] = names[NEW_OBJ];
      result = NEW_OBJ;
    }
    names[LINKER_CALL] = new Name(linker, outArgs);
    lambdaName += "_" + shortenSignature(basicTypeSignature(mtype));
    LambdaForm lform = new LambdaForm(lambdaName, ARG_LIMIT, names, result);
    // This is a tricky bit of code.  Don't send it through the LF interpreter.
    lform.compileToBytecode();
    return lform;
  }

  static Object findDirectMethodHandle(Name name) {
    if (name.function == Lazy.NF_internalMemberName ||
        name.function == Lazy.NF_internalMemberNameEnsureInit ||
        name.function == Lazy.NF_constructorMethod) {
      assert (name.arguments.length == 1);
      return name.arguments[0];
    }
    return null;
  }

  private static void maybeCompile(LambdaForm lform, MemberName m) {
    if (VerifyAccess.isSamePackage(m.getDeclaringClass(), MethodHandle.class))
    // Help along bootstrapping...
    {
      lform.compileToBytecode();
    }
  }

  /**
   * Static wrapper for DirectMethodHandle.internalMemberName.
   */
  @ForceInline
    /*non-public*/ static Object internalMemberName(Object mh) {
    return ((DirectMethodHandle) mh).member;
  }

  /**
   * Static wrapper for DirectMethodHandle.internalMemberName.
   * This one also forces initialization.
   */
    /*non-public*/
  static Object internalMemberNameEnsureInit(Object mh) {
    DirectMethodHandle dmh = (DirectMethodHandle) mh;
    dmh.ensureInitialized();
    return dmh.member;
  }

  /*non-public*/
  static boolean shouldBeInitialized(MemberName member) {
    switch (member.getReferenceKind()) {
      case REF_invokeStatic:
      case REF_getStatic:
      case REF_putStatic:
      case REF_newInvokeSpecial:
        break;
      default:
        // No need to initialize the class on this kind of member.
        return false;
    }
    Class<?> cls = member.getDeclaringClass();
    if (cls == ValueConversions.class ||
        cls == MethodHandleImpl.class ||
        cls == Invokers.class) {
      // These guys have lots of <clinit> DMH creation but we know
      // the MHs will not be used until the system is booted.
      return false;
    }
    if (VerifyAccess.isSamePackage(MethodHandle.class, cls) ||
        VerifyAccess.isSamePackage(ValueConversions.class, cls)) {
      // It is a system class.  It is probably in the process of
      // being initialized, but we will help it along just to be safe.
      if (UNSAFE.shouldBeInitialized(cls)) {
        UNSAFE.ensureClassInitialized(cls);
      }
      return false;
    }
    return UNSAFE.shouldBeInitialized(cls);
  }

  private static class EnsureInitialized extends ClassValue<WeakReference<Thread>> {

    @Override
    protected WeakReference<Thread> computeValue(Class<?> type) {
      UNSAFE.ensureClassInitialized(type);
      if (UNSAFE.shouldBeInitialized(type))
      // If the previous call didn't block, this can happen.
      // We are executing inside <clinit>.
      {
        return new WeakReference<>(Thread.currentThread());
      }
      return null;
    }

    static final EnsureInitialized INSTANCE = new EnsureInitialized();
  }

  private void ensureInitialized() {
    if (checkInitialized(member)) {
      // The coast is clear.  Delete the <clinit> barrier.
      if (member.isField()) {
        updateForm(preparedFieldLambdaForm(member));
      } else {
        updateForm(preparedLambdaForm(member));
      }
    }
  }

  private static boolean checkInitialized(MemberName member) {
    Class<?> defc = member.getDeclaringClass();
    WeakReference<Thread> ref = EnsureInitialized.INSTANCE.get(defc);
    if (ref == null) {
      return true;  // the final state
    }
    Thread clinitThread = ref.get();
    // Somebody may still be running defc.<clinit>.
    if (clinitThread == Thread.currentThread()) {
      // If anybody is running defc.<clinit>, it is this thread.
      if (UNSAFE.shouldBeInitialized(defc))
      // Yes, we are running it; keep the barrier for now.
      {
        return false;
      }
    } else {
      // We are in a random thread.  Block.
      UNSAFE.ensureClassInitialized(defc);
    }
    assert (!UNSAFE.shouldBeInitialized(defc));
    // put it into the final state
    EnsureInitialized.INSTANCE.remove(defc);
    return true;
  }

  /*non-public*/
  static void ensureInitialized(Object mh) {
    ((DirectMethodHandle) mh).ensureInitialized();
  }

  /**
   * This subclass represents invokespecial instructions.
   */
  static class Special extends DirectMethodHandle {

    private Special(MethodType mtype, LambdaForm form, MemberName member) {
      super(mtype, form, member);
    }

    @Override
    boolean isInvokeSpecial() {
      return true;
    }

    @Override
    MethodHandle copyWith(MethodType mt, LambdaForm lf) {
      return new Special(mt, lf, member);
    }
  }

  /**
   * This subclass handles constructor references.
   */
  static class Constructor extends DirectMethodHandle {

    final MemberName initMethod;
    final Class<?> instanceClass;

    private Constructor(MethodType mtype, LambdaForm form, MemberName constructor,
        MemberName initMethod, Class<?> instanceClass) {
      super(mtype, form, constructor);
      this.initMethod = initMethod;
      this.instanceClass = instanceClass;
      assert (initMethod.isResolved());
    }

    @Override
    MethodHandle copyWith(MethodType mt, LambdaForm lf) {
      return new Constructor(mt, lf, member, initMethod, instanceClass);
    }
  }

  /*non-public*/
  static Object constructorMethod(Object mh) {
    Constructor dmh = (Constructor) mh;
    return dmh.initMethod;
  }

  /*non-public*/
  static Object allocateInstance(Object mh) throws InstantiationException {
    Constructor dmh = (Constructor) mh;
    return UNSAFE.allocateInstance(dmh.instanceClass);
  }

  /**
   * This subclass handles non-static field references.
   */
  static class Accessor extends DirectMethodHandle {

    final Class<?> fieldType;
    final int fieldOffset;

    private Accessor(MethodType mtype, LambdaForm form, MemberName member,
        int fieldOffset) {
      super(mtype, form, member);
      this.fieldType = member.getFieldType();
      this.fieldOffset = fieldOffset;
    }

    @Override
    Object checkCast(Object obj) {
      return fieldType.cast(obj);
    }

    @Override
    MethodHandle copyWith(MethodType mt, LambdaForm lf) {
      return new Accessor(mt, lf, member, fieldOffset);
    }
  }

  @ForceInline
    /*non-public*/ static long fieldOffset(Object accessorObj) {
    // Note: We return a long because that is what Unsafe.getObject likes.
    // We store a plain int because it is more compact.
    return ((Accessor) accessorObj).fieldOffset;
  }

  @ForceInline
    /*non-public*/ static Object checkBase(Object obj) {
    // Note that the object's class has already been verified,
    // since the parameter type of the Accessor method handle
    // is either member.getDeclaringClass or a subclass.
    // This was verified in DirectMethodHandle.make.
    // Therefore, the only remaining check is for null.
    // Since this check is *not* guaranteed by Unsafe.getInt
    // and its siblings, we need to make an explicit one here.
    obj.getClass();  // maybe throw NPE
    return obj;
  }

  /**
   * This subclass handles static field references.
   */
  static class StaticAccessor extends DirectMethodHandle {

    final private Class<?> fieldType;
    final private Object staticBase;
    final private long staticOffset;

    private StaticAccessor(MethodType mtype, LambdaForm form, MemberName member,
        Object staticBase, long staticOffset) {
      super(mtype, form, member);
      this.fieldType = member.getFieldType();
      this.staticBase = staticBase;
      this.staticOffset = staticOffset;
    }

    @Override
    Object checkCast(Object obj) {
      return fieldType.cast(obj);
    }

    @Override
    MethodHandle copyWith(MethodType mt, LambdaForm lf) {
      return new StaticAccessor(mt, lf, member, staticBase, staticOffset);
    }
  }

  @ForceInline
    /*non-public*/ static Object nullCheck(Object obj) {
    obj.getClass();
    return obj;
  }

  @ForceInline
    /*non-public*/ static Object staticBase(Object accessorObj) {
    return ((StaticAccessor) accessorObj).staticBase;
  }

  @ForceInline
    /*non-public*/ static long staticOffset(Object accessorObj) {
    return ((StaticAccessor) accessorObj).staticOffset;
  }

  @ForceInline
    /*non-public*/ static Object checkCast(Object mh, Object obj) {
    return ((DirectMethodHandle) mh).checkCast(obj);
  }

  Object checkCast(Object obj) {
    return member.getReturnType().cast(obj);
  }

  // Caching machinery for field accessors:
  private static byte
      AF_GETFIELD = 0,
      AF_PUTFIELD = 1,
      AF_GETSTATIC = 2,
      AF_PUTSTATIC = 3,
      AF_GETSTATIC_INIT = 4,
      AF_PUTSTATIC_INIT = 5,
      AF_LIMIT = 6;
  // Enumerate the different field kinds using Wrapper,
  // with an extra case added for checked references.
  private static int
      FT_LAST_WRAPPER = Wrapper.values().length - 1,
      FT_UNCHECKED_REF = Wrapper.OBJECT.ordinal(),
      FT_CHECKED_REF = FT_LAST_WRAPPER + 1,
      FT_LIMIT = FT_LAST_WRAPPER + 2;

  private static int afIndex(byte formOp, boolean isVolatile, int ftypeKind) {
    return ((formOp * FT_LIMIT * 2)
        + (isVolatile ? FT_LIMIT : 0)
        + ftypeKind);
  }

  private static final LambdaForm[] ACCESSOR_FORMS
      = new LambdaForm[afIndex(AF_LIMIT, false, 0)];

  private static int ftypeKind(Class<?> ftype) {
    if (ftype.isPrimitive()) {
      return Wrapper.forPrimitiveType(ftype).ordinal();
    } else if (VerifyType.isNullReferenceConversion(Object.class, ftype)) {
      return FT_UNCHECKED_REF;
    } else {
      return FT_CHECKED_REF;
    }
  }

  /**
   * Create a LF which can access the given field.
   * Cache and share this structure among all fields with
   * the same basicType and refKind.
   */
  private static LambdaForm preparedFieldLambdaForm(MemberName m) {
    Class<?> ftype = m.getFieldType();
    boolean isVolatile = m.isVolatile();
    byte formOp;
    switch (m.getReferenceKind()) {
      case REF_getField:
        formOp = AF_GETFIELD;
        break;
      case REF_putField:
        formOp = AF_PUTFIELD;
        break;
      case REF_getStatic:
        formOp = AF_GETSTATIC;
        break;
      case REF_putStatic:
        formOp = AF_PUTSTATIC;
        break;
      default:
        throw new InternalError(m.toString());
    }
    if (shouldBeInitialized(m)) {
      // precompute the barrier-free version:
      preparedFieldLambdaForm(formOp, isVolatile, ftype);
      assert ((AF_GETSTATIC_INIT - AF_GETSTATIC) ==
          (AF_PUTSTATIC_INIT - AF_PUTSTATIC));
      formOp += (AF_GETSTATIC_INIT - AF_GETSTATIC);
    }
    LambdaForm lform = preparedFieldLambdaForm(formOp, isVolatile, ftype);
    maybeCompile(lform, m);
    assert (lform.methodType().dropParameterTypes(0, 1)
        .equals(m.getInvocationType().basicType()))
        : Arrays.asList(m, m.getInvocationType().basicType(), lform, lform.methodType());
    return lform;
  }

  private static LambdaForm preparedFieldLambdaForm(byte formOp, boolean isVolatile,
      Class<?> ftype) {
    int afIndex = afIndex(formOp, isVolatile, ftypeKind(ftype));
    LambdaForm lform = ACCESSOR_FORMS[afIndex];
    if (lform != null) {
      return lform;
    }
    lform = makePreparedFieldLambdaForm(formOp, isVolatile, ftypeKind(ftype));
    ACCESSOR_FORMS[afIndex] = lform;  // don't bother with a CAS
    return lform;
  }

  private static LambdaForm makePreparedFieldLambdaForm(byte formOp, boolean isVolatile,
      int ftypeKind) {
    boolean isGetter = (formOp & 1) == (AF_GETFIELD & 1);
    boolean isStatic = (formOp >= AF_GETSTATIC);
    boolean needsInit = (formOp >= AF_GETSTATIC_INIT);
    boolean needsCast = (ftypeKind == FT_CHECKED_REF);
    Wrapper fw = (needsCast ? Wrapper.OBJECT : Wrapper.values()[ftypeKind]);
    Class<?> ft = fw.primitiveType();
    assert (ftypeKind(needsCast ? String.class : ft) == ftypeKind);
    String tname = fw.primitiveSimpleName();
    String ctname = Character.toUpperCase(tname.charAt(0)) + tname.substring(1);
    if (isVolatile) {
      ctname += "Volatile";
    }
    String getOrPut = (isGetter ? "get" : "put");
    String linkerName = (getOrPut + ctname);  // getObject, putIntVolatile, etc.
    MethodType linkerType;
    if (isGetter) {
      linkerType = MethodType.methodType(ft, Object.class, long.class);
    } else {
      linkerType = MethodType.methodType(void.class, Object.class, long.class, ft);
    }
    MemberName linker = new MemberName(Unsafe.class, linkerName, linkerType, REF_invokeVirtual);
    try {
      linker = IMPL_NAMES
          .resolveOrFail(REF_invokeVirtual, linker, null, NoSuchMethodException.class);
    } catch (ReflectiveOperationException ex) {
      throw newInternalError(ex);
    }

    // What is the external type of the lambda form?
    MethodType mtype;
    if (isGetter) {
      mtype = MethodType.methodType(ft);
    } else {
      mtype = MethodType.methodType(void.class, ft);
    }
    mtype = mtype.basicType();  // erase short to int, etc.
    if (!isStatic) {
      mtype = mtype.insertParameterTypes(0, Object.class);
    }
    final int DMH_THIS = 0;
    final int ARG_BASE = 1;
    final int ARG_LIMIT = ARG_BASE + mtype.parameterCount();
    // if this is for non-static access, the base pointer is stored at this index:
    final int OBJ_BASE = isStatic ? -1 : ARG_BASE;
    // if this is for write access, the value to be written is stored at this index:
    final int SET_VALUE = isGetter ? -1 : ARG_LIMIT - 1;
    int nameCursor = ARG_LIMIT;
    final int F_HOLDER = (isStatic ? nameCursor++ : -1);  // static base if any
    final int F_OFFSET = nameCursor++;  // Either static offset or field offset.
    final int OBJ_CHECK = (OBJ_BASE >= 0 ? nameCursor++ : -1);
    final int INIT_BAR = (needsInit ? nameCursor++ : -1);
    final int PRE_CAST = (needsCast && !isGetter ? nameCursor++ : -1);
    final int LINKER_CALL = nameCursor++;
    final int POST_CAST = (needsCast && isGetter ? nameCursor++ : -1);
    final int RESULT = nameCursor - 1;  // either the call or the cast
    Name[] names = arguments(nameCursor - ARG_LIMIT, mtype.invokerType());
    if (needsInit) {
      names[INIT_BAR] = new Name(Lazy.NF_ensureInitialized, names[DMH_THIS]);
    }
    if (needsCast && !isGetter) {
      names[PRE_CAST] = new Name(Lazy.NF_checkCast, names[DMH_THIS], names[SET_VALUE]);
    }
    Object[] outArgs = new Object[1 + linkerType.parameterCount()];
    assert (outArgs.length == (isGetter ? 3 : 4));
    outArgs[0] = UNSAFE;
    if (isStatic) {
      outArgs[1] = names[F_HOLDER] = new Name(Lazy.NF_staticBase, names[DMH_THIS]);
      outArgs[2] = names[F_OFFSET] = new Name(Lazy.NF_staticOffset, names[DMH_THIS]);
    } else {
      outArgs[1] = names[OBJ_CHECK] = new Name(Lazy.NF_checkBase, names[OBJ_BASE]);
      outArgs[2] = names[F_OFFSET] = new Name(Lazy.NF_fieldOffset, names[DMH_THIS]);
    }
    if (!isGetter) {
      outArgs[3] = (needsCast ? names[PRE_CAST] : names[SET_VALUE]);
    }
    for (Object a : outArgs) {
      assert (a != null);
    }
    names[LINKER_CALL] = new Name(linker, outArgs);
    if (needsCast && isGetter) {
      names[POST_CAST] = new Name(Lazy.NF_checkCast, names[DMH_THIS], names[LINKER_CALL]);
    }
    for (Name n : names) {
      assert (n != null);
    }
    String fieldOrStatic = (isStatic ? "Static" : "Field");
    String lambdaName = (linkerName + fieldOrStatic);  // significant only for debugging
    if (needsCast) {
      lambdaName += "Cast";
    }
    if (needsInit) {
      lambdaName += "Init";
    }
    return new LambdaForm(lambdaName, ARG_LIMIT, names, RESULT);
  }

  /**
   * Pre-initialized NamedFunctions for bootstrapping purposes.
   * Factored in an inner class to delay initialization until first usage.
   */
  private static class Lazy {

    static final NamedFunction
        NF_internalMemberName,
        NF_internalMemberNameEnsureInit,
        NF_ensureInitialized,
        NF_fieldOffset,
        NF_checkBase,
        NF_staticBase,
        NF_staticOffset,
        NF_checkCast,
        NF_allocateInstance,
        NF_constructorMethod;

    static {
      try {
        NamedFunction nfs[] = {
            NF_internalMemberName = new NamedFunction(DirectMethodHandle.class
                .getDeclaredMethod("internalMemberName", Object.class)),
            NF_internalMemberNameEnsureInit = new NamedFunction(DirectMethodHandle.class
                .getDeclaredMethod("internalMemberNameEnsureInit", Object.class)),
            NF_ensureInitialized = new NamedFunction(DirectMethodHandle.class
                .getDeclaredMethod("ensureInitialized", Object.class)),
            NF_fieldOffset = new NamedFunction(DirectMethodHandle.class
                .getDeclaredMethod("fieldOffset", Object.class)),
            NF_checkBase = new NamedFunction(DirectMethodHandle.class
                .getDeclaredMethod("checkBase", Object.class)),
            NF_staticBase = new NamedFunction(DirectMethodHandle.class
                .getDeclaredMethod("staticBase", Object.class)),
            NF_staticOffset = new NamedFunction(DirectMethodHandle.class
                .getDeclaredMethod("staticOffset", Object.class)),
            NF_checkCast = new NamedFunction(DirectMethodHandle.class
                .getDeclaredMethod("checkCast", Object.class, Object.class)),
            NF_allocateInstance = new NamedFunction(DirectMethodHandle.class
                .getDeclaredMethod("allocateInstance", Object.class)),
            NF_constructorMethod = new NamedFunction(DirectMethodHandle.class
                .getDeclaredMethod("constructorMethod", Object.class))
        };
        for (NamedFunction nf : nfs) {
          // Each nf must be statically invocable or we get tied up in our bootstraps.
          assert (InvokerBytecodeGenerator.isStaticallyInvocable(nf.member)) : nf;
          nf.resolve();
        }
      } catch (ReflectiveOperationException ex) {
        throw newInternalError(ex);
      }
    }
  }
}
